Reciprocating pumps



Nov. 20, 1962 R. N. KNIGHTS 3,064,582 7 RECIPROCATING PUMPS Filed June 6, 1960 4 Sheets-Sheet 1 INvEN'roR R/C'HARD IV. XIV/6,4725

ATTORNEYS Filed June 6, 1960 4 Sheets-Sheet 2 INVENTOR R/CHAED M Hw /r5 A'r'roRNEN Nov. 20, 1962 R. KNIGHTS 3,064,582

RECIPROCATING PUMPS Filed June 6, 1960 4 Sheets-Sheet 3 I 68 m I 73 INVE NToR P/(WAED M (MIG/1'76 Nov. 20, 1962 R. N. KNIGHTS 3,064,582

RECIPROCATING PUMPS Filed June 6. 1960 4 Sheets-Sheet 4 INVENTOR RKHARD N. mv/a/rs' ATTORNEYS Patented Nov. 20, 1962 3,064,582 RECIIRUCATING PUMPS Richard N. Knights, Hucclecote, England, assignor to Dowty Rotol Limited, Cheltenham, England, a British company Filed Jane 6, 196-9, Ser. No. 34,211 Claims priority, application Great Britain June 12, 1959 3 Claims. (Cl. 103-44) This invention relates to a reciprocating pump of the kind having a flexible diaphragm which separates the liquid to be pumped from the liquid which actuates the diaphragm reciprocally.

The object of the invention is to provide an improved construction of pump of this kind which is particularly suitable for pumping liquid suspensions of abrasive material, or for pumping corrosive liquids.

According to the invention a reciprocating pump for such liquids comprises a cylinder, a piston arranged to be reciprocated in the cylinder under the pressure of an actuating liquid, a flexible diaphragm separated from that face of the piston which is remote from the actuating liquid and which contains with said face a liquid-filled chamber of substantially fixed volume, and a pumping chamber on the other side of the flexible diaphragm arranged to receive the liquid to be pumped by the action of the piston through the liquid in the chamber of substantially fixed volume upon the flexible diaphragm.

According to a feature of the invention, a vent valve is provided responsive to fiexure of the diaphragm on the pumping stroke beyond a given limit and opening at this limit to release liquid from the substantially fixed volume chamber if the diaphragm tends to flex beyond said limit.

In a preferred construction the piston is one of two pistons which are movable together and act alternately through substantially fixed volumes of liquid upon two flexible diaphragms.

The invention is illustrated in the accompanying drawings of which:

FIGURE 1 is a plan view of a pump suitable for pumping liquid mud with part of the working mechanism shown in section,

FIGURE 2 is a side elevation, the upper half of which is a section on the line DD of FIGURE 1,

FIGURE 2a is an enlarged detail from FIGURE 2,

FIGURE 3 is a central section on the line C-C of FIGURE 1,

FIGURE 4 is a section on the line A--A of FIG- URE 1,

FIGURE 5 is a section on the line BB of FIG- URE 1, and

FIGURES 6 and 7 are sectional diagrams of the pump at different stages of operation.

The pump comprises a central valve housing 10 formed at opposite ends with co-axial bores 11 and 12 in which are fitted replaceable cylinder liners 13 and 14. Pistons 15 and 16 provided with sealing rings 17 are slidably mounted in the respective cylinders 13 and 14, and connected for movement in unison by three equally spaced connecting rods 25, which pass slidably through and are suitably sealed with respect to the valve housing 10. The pistons 15 and 16 are arranged to be reciprocated hydraulically under the control of a pilot valve and a main valve in the housing 10. The pilot valve comprises a cylindrical bore 18 parallel to the axis of the housing 10 and a valve spool 19 slidable therein. The spool 19 has tail rods 21 and 22 at opposite ends which are engageable by the pistons 15 and 16 respectively towards the ends of their reciprocating strokes so as to shift the valve spool 19 from one end position to another. The pilot valve controls a main valve comprising a cylindrical bore 23 on the central axis of the housing 10 and a valve spool 24 slidable therein.

A liquid pressure inlet 26 in the housing 10, see FIG- URE 3, leads to pressure grooves 27 and 28 in the bores 18 and 23 of the pilot and main valves respectively, and a low pressure outlet 29 connects with axially separated grooves 31, 32 and 33, 34 in the respective bores 18 and 23. Axially separated grooves 35 and 36 in the bore 18 lead through passages 37 and 38 to grooves 39 and 41 at the upper and lower ends of the main valve bore 23. Axially separated grooves 42 and 43 in the main valve bore 23 lead through passages 44 and 45 in the housing 10 to chambers 40 and 50 enclosed between the respective pistons 15 and 16 and the housing 10. These passages 44 and 45 are readily seen in the diagrams of FIGURES 6 and 7, and the passage 45 is shown in the section of FIGURE 4. The pilot valve spool 19 is formed with three axially separated lands 46, 47 and 48, and the main valve spool 24 is formed with three axially separated lands 49, 51 and 52. The main valve spool 24 has counter-bored ends 53 with small cross drillings 54. Each end is engageable over a fitting spigot 55 whereby the terminal movement of the main spool 24 is cushioned by the discharge of hydraulic liquid through the cross drilling 54.

The operation of the mechanism as thus far described is as follows. The pilot valve spool 19 is hydraulically balanced and fits the bore 18 sufficiently tightly to stay in one end position or the other. As shown in FIG- URE 1, the pressure groove 27 is open between the lands 46 and 47 to the groove 35 so that pressure has access through the passage 37 to the groove 39 at one end of the main valve spool 24. The spool 24 is thus maintained in one end position whereby pressure liquid from the groove 28 has access through the groove 42 and passage 44 to the chamber 40, while the opposite chamber 50 opens through the passage 45 to the groove 43 and between the lands 51 and 52 to the low pressure groove 34. The piston assembly 15, 16, 25 therefore moves upwardly with respect to FIGURE 1 until near the end of its stroke the piston 16 engages the tail rod 22 and shifts the pilot valve spool 19 over to the position in the diagram of FIGURE 6.

Pressure liquid from the groove 27 now passes between the lands 47 and 48 to the groove 36, and thence through the passage 38 to the groove 41 at one end of the main valve spool 24. Simultaneously the groove 39 at the other end of the main valve spool opens through the passage 37 and groove 35, between lands 46 and 47 to the low pressure groove 31 which is in communication with the low pressure outlet 29. The main valve spool 24 then moves upwardly with respect to FIGURE 6 where the lands 51 and 52 are about to connect the pressure groove 28 with the groove 43, and the lands 49 and 51 are about to connect the low pressure groove 33 with the groove 42. The chamber 56 is then connected to high pressure at the inlet 26 while the chamber 40 is connected to low pressure at the outlet 29 whereupon the piston assembly 15, 16, 25 moves in the reverse direction. At the end of its stroke the piston 15 shifts the valve spool 19 over to the position shown in FIGURE 7, thus causing the main valve spool 24 to move over whereby the pressure and return connections to the chambers 49 and 50 are again reversed. Thus the pilot valve and main valve cause the pistons 15, 16 to reciprocate back and forth automatically under liquid pressure at the inlet 26.

The construction by which the reciprocating pistons 15 and 16 are arranged to pump liquid suspensions of solids such as mud will now be dsecribed. End housings 56 and 57 attached to the central valve housing 10 the piston '75 to close the valve.

have cavities 58 and 59 which open into cylinders 60 and 61 forming part of the respective housings 56 and 57. As the construction is a symmetrical one, only the one half shown in section in FIGURE 2 will be described. The cylinder 60 is divided by a thin flexible diaphragm 62 into a hydraulic liquid chamber 63 and 'a pumping chamber 64.

The cylinder 6% is closed atone end by a cap 65 having a centrally arranged vent valve 66 which is openable by a tension element provided by a cord 67 attached to the centre of the diaphragm 62, this cord 67 acting in tension on the valve 66 when the diaphragm 62 is flexed at a permissible maximum volume of the hydraulic liquid chamber 63. The valve 66 shown on a larger scale in FIGURE 2a comprises an inwardly directed boss 68 having behind it an opening 69 from the chamber 63. The opening 69 leads to a valve seat 71, and a bore 72 in which a cylindrical sleeve 73 is fixed, while a movable valve member comprises a valve head 74 engageable with the seat 71 and a piston 75 slidable in the sleeve 73. The diameter of the piston 75 is equal to the diameter of the seat 71 whereby the movable member is balanced hydraulically, but a spring 76 is interposed between the sleeve 73 and Vent holes 77 in the boss 68 lead from the bore 72 to the exterior of the cap 65.

An inlet '78 for liquid mud at the centre of the housing opens through a non-return inlet valve 7? into a passage 81 which leads to the mud chamber 64, see FIGURE 5.

The .passage 81 also opens through a non-return outlet valve 82 to an outlet 83 in the housing 10. The valves 79 and-82 are spring-loaded on to replaceable seating rings 84 and '85, and .the complete valve assemblies are accessible through covers 86 and 87 respectively. Covers 88 and 89 enclose similar non-return valves leading to and from a mud chamber in the cylinder '61. The inlet 78 and outlet 83 are common to both mud chambers wherein the pumping takes place alternately upon reciprocation of the pistons and 16.

The pumping of mud in the chamber 64 takes place under the action of a substantially constant volume of hydraulic liquid in a chamber formed between the piston 15 and the diaphragm 62. The volume is such that the diaphragm 62 will flex equally on opposite sides of its midway position, and its maximum possible volumetric displacement is substantially greater than full volumetric displacement of the pistons 15 and 16 whereby the diaphragm 62 will not become distended with consequent risk of rupture at the extreme limits of its stroke.

The pistons 15 and 16 provide by means of the packing rings 17 a sliding seal against the cylinder liners 14, so that if after prolonged use there tends to be a leal age of hydraulic liquid from the chambers 46 and 47 across the rings 17, the volume of liquid between the pistons 15 and 16, and the diaphragm 62 will increase. A feature of the invention is that this volume is prevented from increasing beyond a prescribed amount in order to prevent the risk of rupturing the diaphragms at the end of their pumping strokes. This safeguard is provided by the cord 67 which is pulled tight by the diaphragm 64 before the latter reaches the safe limit of flexure at the end of its pumping stroke. The cord 67 then pulls the valve head 74 off its seat 71 and allows a quantity of excess hydraulic liquid to be vented to the outside of the cap 65 whereby a safe volume of liquid is maintained. The rate at which liquid accumulates in either cap 65 indicates whether the sealing rings 17 and cylinder liners 14 require inspection and replacement.

Each diaphragm 62 is subject to negligible pressure difierences across it so it can be thin, thereby decreasing the internal stresses in the material upon flexure and increasing its working life. If for any reason the diaphragm ruptures, the reciprocating mechanism in the housing 10 is substantially safeguarded from penetration of the liquid mud, which may be abrasive, by the piston All 15 or 16 as the case may be until the rupture is discovered in the course of routine inspection.

The actuating liquid may be supplied to the high pressure inlet 26 by a variable delivery pump shown diagrammatically at 90 in FIGURE 3. If the pump 9'0 is driven at constant power input the delivery can be varied to give a large flow at a relatively low pressure or a small flow at a relatively high pressure, and the output of the reciprocating pump will vary accordingly. This is of particular advantage when the reciprocating pump is used to supply mud to an earth boring rig because the variation of delivery described is required as the drilling proceeds to greater depths.

The ratio of the pressure of the actuating liquid on one ide of each piston 15 or 16 to the liquid pressure on the other side is dependent upon the ratio or" the respective areas. The latter ratio may be selected in designing the pump by means of the total effective area of the tie rods 25. Alternatively, a stepped piston may be provided.

I claim as my invention:

1. A reciprocating pump for liquids comprising two co-axial cylinders, a piston assembly including two pistons mounted for reciprocal movement together in the respective cylinders, a reversing valve including an inlet adapted for connection with a source of actuating liquid, two passages each of which is connected with one of said cylinders, and valve-operating means co-acting with the piston assembly upon reciprocal movement of the latter to reverse the connection of said'inlet with the said two passages whereby the piston assembly is reciprocable automatically under the pressure of the source of actuating liquid, a flexible diaphragm mounted in spaced relation from that face of each piston which is remote from the actuating liquid, a liquid-filled chamber disposed between each piston and the flexible diaphragm associated therewith, the liquid therein forming a transmission medium operative to flex the diaphragm reciprocally in accordance with the reciprocatory motion of said piston, a vent valve connected to each liquid-filled chamber, an operating element for each vent valve disposed for displacement by the diaphragm upon flexure of said diaphragm beyond a given limit caused by the pressure stroke of the associated piston, said element being operative at this limit to open the vent valve and release any excess of liquid in said chamber whereby the diaphragm is restored to said limit, and for each diaphragm a pumping chamber disposed on the other side of the diaphragm from said liquid-filled chamber, said reversing valve comprising a main valve having a valve spool operative in its end positions to connect the inlet for actuating liquid respectively with the passage connected to one cylinder or the passage connected to the other cylinder, pressure responsive means operative upon the valve spool, and a pilot valve having a valve spool operative in its end positions to connect the inlet for actuating liquid with said pressure responsive means so as to displace the main valve spool to one end position or the other, said pilot valve spool being adapted for co-operative two-way engagement with the piston assembly so as to be displaceable into one end position or the other upon completion of each reciprocating stroke of the piston assembly.

2. A reciprocating pump for liquids comprising two co-axial cylinders, a piston assembly including two pistons mounted for reciprocal movement together in the respective cylinders, a reversing valve including an inlet adapted for connection with a source of actuating liquid, two passages each of which is connected with one of said cylinders, and valve-operating means co-acting with the piston assembly upon reciprocal movement of the latter to reverse the connection of said inlet with the said two passages whereby the piston assembly is reciprocable automatically under the pressure of the source of actuating liquid, a flexible diaphragm mounted in spaced relation from that face of each piston which is remote from the actuating liquid, a liquid-filled chamber disposed between each piston and the flexible diaphragm associated therewith, the liquid therein forming a transmission medium operative to flex the diaphragm reciprocally in accordance with the reciprocatory motion of said piston, a vent valve connected to each liquidfilled chamber, an operating element for each vent valve disposed for displacement by the diaphragm upon fiexure of said diaphragm beyond a given limit caused by the pressure stroke of the associated piston, said element being operative at this limit to open the vent valve and release any excess of liquid in said chamber whereby the diaphragm is restored to said limit, and for each diaphragm a pumping chamber disposed on the other side of the diaphragm from said liquidfillcd chamber, the said reversing valve being mounted in a housing disposed between the two co-axial cylinders, the two pistons which are mounted in said cylinders being connected together by tie rods which pass through the housing.

3. A reciprocating pump for liquids comprising two fixed cylinders each having an inward and an outward end, a piston assembly including two pistons mounted in the respective cylinders between the inward and outward ends thereof, and connecting means extending from one piston through the inward ends of the two cylinders to the other piston to co-ordinate reciprocal inward and outward movements of one piston in its cylinder with reciprocal outward and inward movements respectively of the other piston in its cylinder, said connecting means having opposite end portions within the cylinders of uniform finite cross-sectional area whereby the effective area of the inner end of each piston is less than the elfective area of the outer end, two passages each of which is connected with one of said cylinders at a position behind the inner end of the piston mounted therein, a reversing valve including an inlet for connection with a source of actuating liquid under pressure and arranged to connect said inlet to one or the other of said passages, and valve-operating means arranged for operation by the piston assembly upon reciprocal movements of the pistons in their cylinders to connect said inlet with one such passage, and to cyclically reverse the connection of said inlet with the said two passages, whereby the piston is reciprocable automatically under the pressure of the liquid source applied to the inner ends of the pistons in turn, a diaphragm chamber disposed at the outward end of each cylinder including a flexible diaphragm dividing said chamber into two parts, one of said parts adjoining the cylinder, said one part, be tween the outer end of the piston and the diaphragm, being adapted to contain a substantially constant trapped volume of liquid which constitutes a pressure transmitting medium actuated by reciprocation of the piston to flex the diaphragm alternately outwardly from the cylinder and inwardly, a vent valve communicating with the part of each diaphragm chamber that contains the liquid pressure transmitting medium, said vent valve comprising an opening from said chamber communicating with low pressure, a movable valve element normally closing said opening, and a valve-operating element arranged for op eration in response to outward flexure of the diaphragm beyond a given limit to displace the movable valve-element from the opening for releasing liquid transmitting medium in excess of the substantially constant trapped volume, an inlet valve communicating with the other part of said chamber and adapted for connection with the source of liquid to be pumped and an outlet valve for pumped liquid also communicating with such other part of the chamber, and a common outlet for pumped liquid connected to the outlet valves of both diaphragm chambers.

References Qited in the file of this patent UNITED STATES PATENTS 862,867 Eggleston Aug. 6, 1907 900,357 Davis Oct. 6, 1908 2,296,647 McCormick Sept. 22, 1942 2,732,897 Parsegian Jan. 31, 1956 2,927,431 Pitts Mar. 8, 1960 

